The present invention relates generally to dual voltage automotive vehicles, and more specifically, to charging the batteries of the electrical systems of the vehicle.
Automotive vehicles with internal combustion engines are typically provided with both a starter motor and alternator. In recent years, a combined alternator and starter motor has been proposed. Such systems have a rotor mounted directly to the crankshaft of the engine and a stator sandwiched between the engine block and the bell housing of the transmission. During initial startup of the vehicle, the starter/generator functions as a starter. While functioning as a starter, the starter/generator rotates the crankshaft of the engine while the cylinders are fired.
After the engine is started, the starter/generator is used as a generator to charge the electrical system of the vehicle.
Such systems may include both a 12-volt nominal system and a 36-volt nominal system, which correspond to 14 and 42-volt operating voltages, respectively. It should be noted the dual voltage systems may also be incorporated in vehicles without starter/generators.
Electrical energy from the 42-volt battery of the vehicle is used to turn the starter/generator, which in turn is used to start the motor. Energy from the 12-volt system may be used to operate the vehicle lights and instrument panel. Consequently, it is important to maintain the battery so that a certain state of charge is provided to allow the battery to provide enough power to the starter/generator to start the engine. If one or both of the batteries is low, however, the vehicle may need to be jumpstarted. Typical jumpstarting is desirable, wherein jumper cables are connected between a good battery or power source and the discharged battery. Typically, if the 42-volt battery is low it may not be charged by charging the 12-volt battery. It may not be desirable to allow the operator to charge both batteries independently to prevent mixing the voltage potentials and possibly damaging the batteries or the electrical systems.
It would therefore be desirable to provide a method and apparatus for charging a battery to provide an indication to the vehicle operator to guide the operator through the charging process.
The present invention provides a way in which to charge the vehicle batteries so that both batteries of both voltage levels become charged.
In one aspect of the invention, a method of charging a high voltage battery includes electrically coupling a first low voltage source to a low voltage battery, converting the low voltage to a high voltage, charging a high voltage battery with the high voltage, monitoring a state of charge of the high voltage battery, comparing the state of charge to a predetermined state of charge, and generating an indicator when the state of charge reaches the predetermined state of charge.
In a further aspect of the invention, a system for an automotive vehicle includes a low voltage battery having a low voltage, a high voltage battery having a high voltage, and a DC-to-DC converter coupled to the low voltage battery and the high voltage battery. A controller controls a conversion of the low voltage to a high voltage through the DC-to-DC converter and controls the charging of the high voltage battery with the high voltage. The controller monitors a state of charge of the high voltage battery, compares the state of charge to a predetermined state of charge, and generates an indicator when the state of charge reaches the predetermined state of charge.
One advantage is that the indicator may provide to the vehicle operator both instructions and the state of charge of both vehicle batteries.
Other advantages and features of the present invention will become apparent when viewed in light of the detailed description of the preferred embodiment when taken in conjunction with the attached drawings and appended claims.